Question

the effective resistance of two resisotrs in parallel is 7.5ohm . their effective resistance in series is 40 ohm . claculate their individual resistance of resistors

Answer 1

Let the two resistors be R₁ and R₂.

According to question,

In parallel combination, R₁R₂/(R₁+R₂) = 7.5 Ω ……………(1)

In series combination, R₁+R₂ = 40 Ω ………………….(2)

(1) and (2) => R₁R₂ = 7.5×40 = 300

Now,

(R₁-R₂)² = (R₁+R₂)² – 4R₁R₂

=> R₁-R₂ = 20

So,

R₁ = 30 Ω

R₂ = 10 Ω